murmur_git: Fix

[infinisil]

Was failing with the following error when running a service with it:

ServerDB: Database driver QSQLITE not available

This fix is only needed for the git version of murmur.

Ping @jgeerds

Motivation for this change

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after): +0.0002%
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.

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[infinisil]

Ping @wkennington

[infinisil]

I have verified that this fixes the issue with my own murmur NixOS module here (might upstream later)